The present invention relates to an antenna device according to the preamble of claim 1. The invention also relates to a method for manufacturing an antenna device according to the preamble of claim 12.
Common techniques in manufacturing of antenna elements includes either the use a thin self supportive metal sheet having a desired shape, or creating a radiating pattern in a metal coating, supported by a substrate, e.g. by etching, or applying a radiating pattern to a substrate, e.g. by screen printing conducting paint.
These types of antenna elements are usually flexible and may easily be mounted to a mobile telephone.
The metal sheet, or radiating pattern, normally used is made of copper or a copper alloy. The copper oxidises over time and normally there is a need to have a portion of the antenna element connected to some other equipment, e.g. a conductive connection. This connection portion may be plated with another metal to avoid the oxidation and to obtain a good contact with low contact resistance, by for instance gold. This is an expensive process, since gold is expensive.
In DD 146 873, there is described a device for improving the performance of an electrical switch by coating the copper with graphite. By adding the graphite coating the oxidation of the copper is prevented and a good contact between two adjacent circuits on a PCB may be achieved by using a push-button switch over the graphite coated adjacent circuits.
The present invention seeks to provide an improved antenna device.
According to an aspect of the present invention, there is provided an antenna device as specified in claim 1.
The invention is also directed to a method by which an embodiment of the desired antenna device is manufactured.
An advantage of having a graphite compound at least partially coating an antenna device in the present invention is that it prevents the coated conductive pattern to oxidise.
Another advantage of having the graphite coating in the present invention is that it provides a protective layer for the antenna element, since the graphite has sliding properties.
An advantage with an embodiment of the present invention is that the graphite compound provides a contact portion with a low contact resistance compared to without a graphite compound, since the graphite compound prevents the coated conductive pattern to oxidise and the soft graphite compound shapes it self around a contact device, e.g. a contact pin or waveguide shim.
Another advantage is that the inventive antenna device can be used in MID technology with decreased risk of oxidation of conductors.
Another advantage with a further embodiment of the present invention is that the soft graphite compound may be applied to a conductive pattern, which is arranged on a flexible substrate, which is to be bent.
An advantage with the manufacturing method is that the manufacturing steps are reduced when using the graphite compound as a film, where the graphite compound is applied in the shape of the conductive pattern.